Analysis and nonlinear simulation of a quadrupole wiggler FEL at millimeter wavelengths

The use of a helical quadrupole wiggler field in a circular guide for amplification of millimeter waves is discussed. The effects of space charge and axial field are considered for beam stability for near-axis orbits. When space charge is neglected, the orbit equations and properties and characteristic betatron oscillation of frequencies are examined by a linearization of the orbit equations. A nonlinear simulation code for dipole wigglers is modified to examine optimum gain TE/sub 21/ waveguide modes for a quadrupole wiggler in the 30-300 GHz range.<
>